The accumulation of ice on the, wings, flaps, and other control surfaces of an aircraft may be detrimental to the performance of the aircraft. As such, many aircraft include anti-icing systems for preventing or reducing the accumulation of ice during flight. For example, aircraft can include a pneumatic anti-icing system that directs heated air to the flaps and other control surfaces in order to prevent or reduce icing of those surfaces. Alternatively, aircraft may include an electrical anti-icing system that relies upon resistors embedded in the surface of the aircraft to heat the respective surfaces as current flows therethrough.
With respect to a pneumatic anti-icing system, heated air is directed to the wing leading edge or control surfaces of the aircraft. For example, the heated air serves to heat the leading edges to prevent or reduce the accumulation of ice thereupon. The heated air that is utilized by a pneumatic anti-icing system may be, for example, bleed air that is extracted from the aircraft engine. However, the heated air may have a temperature that is so high that the ductwork required to route the heated air to the flaps or other control surfaces must be made of materials that are specifically adapted to withstand such elevated temperatures, thereby increasing the cost of the ductwork. In order to reduce the temperature of the heated air and to avoid requirements for the ductwork to be made of a material specifically designed to withstand greater temperatures and to allow for safe circulation of the heated air through the fuel-filled wings, the heated air bled from the aircraft engine may be cooled, such as from a temperature of about 1000° F. upon exiting the aircraft engine to a temperature of about 450° F. or less.
As such, a pneumatic anti-icing system may include a pre-cooler, such as a radiator over which the heated air is passed, in order to reduce the temperature of the heated air prior to delivery of the heated air to the flaps or other control surfaces. The pre-cooler is at least sometimes located in the ductwork through which the heated air is directed. Although the pre-cooler is able to cool the bleed air extracted from the aircraft engine to a suitable temperature for anti-icing purposes, the elevated temperature of the bleed air may cause the size of the pre-cooler to be increased which, in turn, may cause the size of the ductwork in which the pre-cooler is disposed to correspondingly increase. Since space onboard an aircraft is limited, any increase in the size of the ductwork may be disadvantageous.
Additionally, pneumatic anti-icing systems may sometimes weigh more and be more complex than is desirable for smaller aircraft. Even with larger aircraft, a pneumatic anti-icing system may adversely impact the design requirements. In this regard, a multi-engine aircraft may be designed such that in an instance in which bleed air cannot be extracted from one of the aircraft engines, the flight can continue even if flying in icing conditions by channeling bleed air from the other aircraft engine to the flaps and/or control surfaces in order to prevent or reduce the ice accumulation upon the flaps and other control surfaces. In this scenario, the size of both of the aircraft engines may have to be increased in order to provide for continued anti-icing capabilities in the event that one of the engines is not available to provide bleed air, thereby correspondingly increasing the cost and weight of the aircraft engines.
Regarding an electric anti-icing system, the flaps and other control surfaces of an aircraft may include resistors embedded therein. By causing electrical current to flow through the resistors, heat is generated to prevent or reduce the accumulation of ice on the flaps and other control surfaces. The electrical current that flows through the resistors is generated by the rotation of the high pressure shaft of the aircraft engine, thereby adding to the load of the core gas turbine engine. As a result, the design of the aircraft engine must therefore take into account the additional load on the core gas turbine engine created by the provision of electrical current to the anti-icing system, thereby causing the size, weight and cost of the aircraft engine to be disadvantageously increased in some instances. Additionally, the provision of energy from the core gas turbine engine to the anti-icing system may also cause the pilot to increase the engine speed which may be disadvantageous during descent or while in a holding pattern.